'\" te
.\" Copyright (c) 2007, Sun Microsystems, Inc.  All Rights Reserved
.\" Copyright 1989 AT&T
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
.TH SHMCTL 2 "Apr 10, 2007"
.SH NAME
shmctl \- shared memory control operations
.SH SYNOPSIS
.LP
.nf
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

\fBint\fR \fBshmctl\fR(\fBint\fR \fIshmid\fR, \fBint\fR \fIcmd\fR, \fBstruct shmid_ds *\fR\fIbuf\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBshmctl()\fR function provides a variety of shared memory control
operations as specified by \fIcmd\fR. The permission required for a shared
memory control operation is given as {\fItoken\fR}, where \fItoken\fR is the
type of permission needed. The types of permission are interpreted as follows:
.sp
.in +2
.nf
00400    READ by user
00200    WRITE by user
00040    READ by group
00020    WRITE by group
00004    READ by others
00002    WRITE by others
.fi
.in -2

.sp
.LP
See the \fIShared Memory Operation Permissions\fR section of \fBIntro\fR(2) for
more information.
.sp
.LP
The following operations require the specified tokens:
.sp
.ne 2
.na
\fB\fBIPC_STAT\fR\fR
.ad
.RS 14n
Place the current value of each member of the data structure associated with
\fIshmid\fR into the structure pointed to by \fIbuf\fR. The contents of this
structure are defined in \fBIntro\fR(2). {\fBREAD\fR}
.RE

.sp
.ne 2
.na
\fB\fBIPC_SET\fR\fR
.ad
.RS 14n
Set the value of the following members of the data structure associated with
\fIshmid\fR to the corresponding value found in the structure pointed to by
\fIbuf\fR:
.sp
.in +2
.nf
shm_perm.uid
shm_perm.gid
shm_perm.mode	/* access permission bits only */
.fi
.in -2

This command can be executed only by a process that has appropriate privileges
or an effective user \fBID\fR equal to the value of \fBshm_perm.cuid\fR or
\fBshm_perm.uid\fR in the data structure associated with \fIshmid\fR.
.RE

.sp
.ne 2
.na
\fB\fBIPC_RMID\fR\fR
.ad
.RS 14n
Remove the shared memory identifier specified by \fIshmid\fR from the system.
The segment referenced by the identifier will be destroyed when all processes
with the segment attached have either detached the segment or exited. If the
segment is not attached to any process when \fBIPC_RMID\fR is invoked, it will
be destroyed immediately. This command can be executed only by a process that
has appropriate privileges or an effective user ID equal to the value of
\fBshm_perm.cuid\fR or \fBshm_perm.uid\fR in the data structure associated with
\fIshmid\fR.
.RE

.sp
.ne 2
.na
\fB\fBSHM_LOCK\fR\fR
.ad
.RS 14n
Lock the shared memory segment specified by \fIshmid\fR in memory. This command
can be executed only by a process that has appropriate privileges.
.RE

.sp
.ne 2
.na
\fB\fBSHM_UNLOCK\fR\fR
.ad
.RS 14n
Unlock the shared memory segment specified by \fIshmid\fR. This command can be
executed only by a process that has appropriate privileges.
.RE

.sp
.LP
A shared memory segment must be explicitly removed using \fBIPC_RMID\fR before
the system can deallocate it and the resources it uses.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is
returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
.sp
.LP
The \fBshmctl()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEACCES\fR\fR
.ad
.RS 13n
The \fIcmd\fR argument is equal to \fBIPC_STAT\fR and \fB{READ}\fR operation
permission is denied to the calling process.
.RE

.sp
.ne 2
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 13n
The \fIbuf\fR argument points to an illegal address.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 13n
The \fIshmid\fR argument is not a valid shared memory identifier; or the
\fIcmd\fR argument is not a valid command or is \fBIPC_SET\fR and
\fBshm_perm.uid\fR or \fBshm_perm.gid\fR is not valid.
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 13n
The \fIcmd\fR argument is equal to \fBSHM_LOCK\fR and there is not enough
memory, or the operation would exceed a limit or resource control on locked
memory.
.RE

.sp
.ne 2
.na
\fB\fBEOVERFLOW\fR\fR
.ad
.RS 13n
The \fIcmd\fR argument is \fBIPC_STAT\fR and \fIuid\fR or \fIgid\fR is too
large to be stored in the structure pointed to by \fIbuf\fR.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 13n
The \fIcmd\fR argument is equal to \fBIPC_RMID\fR or \fBIPC_SET\fR, the
effective user ID of the calling process is not equal to the value of
\fBshm_perm.cuid\fR or \fBshm_perm.uid\fR in the data structure associated with
\fIshmid\fR, and {\fBPRIV_IPC_OWNER\fR} is not asserted in the effective set of
the calling process.
.sp
The \fIcmd\fR argument is equal to \fBSHM_LOCK\fR or \fBSHM_UNLOCK\fR and
{\fBPRIV_PROC_LOCK_MEMORY\fR} is not asserted in the effective set of the
calling process.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR ipcs (1),
.BR Intro (2),
.BR shmget (2),
.BR shmop (2),
.BR attributes (7),
.BR privileges (7),
.BR standards (7)
